Shock absorbing apparatus for heavy loads

ABSTRACT

Apparatus for absorbing the shock of a relatively large, movable load, such as a ship striking a dock or the like. The apparatus includes a loadreceiving buffer comprised of a fluid piston and cylinder assembly, the buffer being in fluid communication with a hydro-pneumatic accumulator through first and second fluid flow paths. When a force is exerted on the buffer, fluid flows therefrom through one of said paths and part of the kinetic energy is stored in the accumulator with the greater portion dissipated as heat. The buffer is restored to its initial position by fluid flow from the accumulator to the buffer along the second path. The system operates to assure that the buffer will exert a substantially constant reactive force regardless of displacement to thereby assure dissipation of the kinetic energy with an efficiency approaching 100 percent and with a minimum storage of potential energy.

United States Patent [191 Johnston SHOCK ABSORBING APPARATUS FOR HEAVYLOADS [75] Inventor: James G. Johnston, Willits, Calif. [73] Assignee:Stanray Corporation, Chicago, Ill.

[22] Filed: Mar. 16, 1973 [21] Appl. No.: 341,812

[52] US. Cl 267/116, 267/139, 267/65 R [51] Int. Cl F16f 5/60 [58] Fieldof Search 267/139, 116, 65 R [56] References Cited UNITED STATES PATENTS3,433,474 3/1969 Pirel 267/65 3,494,606 2/1970 Hanchen 267/116 PrimaryExaminer.lames B. Marbert 1 Dec. 17, 1974 5 7] ABSTRACT Apparatus forabsorbing the shock of a relatively large, movable load, such as a shipstriking a dock or the like. The apparatus includes a loadreceivingbuffer comprised of a fluid piston and cylinder assembly, the bufferbeing in fluid communication with a hydropneumatic accumulator throughfirst and second fluid flow paths. When a force is exerted on thebuffer, fluid flows therefrom through one of said paths and part of thekinetic energy is stored in the accumulator with the greater portiondissipated as heat. The buffer is restored to its initial position byfluid flow from the accumulator to the buffer along the second path. Thesystem operates to assure that the buffer will exert a substantiallyconstant reactive force regardless of displacement to thereby assuredissipation of the kinetic energy with an efficiency approaching 100percent and with a minimum storage of potential energy.

12 Claims, 3 Drawing Figures SHOCK ABSORBING APPARATUS FOR HEAVY LOADSThis invention relates to improvements in shock absorbing devices of thetype for dissipating or storing the energy due to the deceleration oflarge masses, such as the engagement of a large ship with a dockstructure.

BACKGROUND OF THE INVENTION When a large ship is docked, it oftentimesexerts large forces on the dock structure. Some such loads on the dockstructure can be large enough to cause structural damage thereto. It isnecessary, therefore, to dissipate the kinetic energy of the shipefficiently with a minimum of structural damage.

Generally, there are two types of devices now in use for handling theshocks caused by ships being docked. The first is a rubber spring whichcan be of any one of a number of different configurations. However, thistype of device has a basic drawback, namely, that the spring absorbs andstores potential energy with an efficiency generally not exceeding 60percent. As the deflection or deformation of the spring increases, thereactive force of the spring increases proportionately. Therefore, thesystem is inefficient because the reactive force is directly related tothe deflection.

Another type of conventional shock absorbing device is a hydraulic unithaving either a fixed orifice or constantly decreasing orifice. Thefixed orifice unit is similar to the spring type mentioned above withrespect to efficiency because, if the velocity of the mass reducesduring dissipation of its kinetic energy, the resistance or reactiveforce reduces accordingly. In addition, the resistance at any timeduring such energy dissipation is directly related to velocity. Thismeans that too large a reactive force can be exerted on the mass at highvelocity or too small a force can be exerted on it at low velocity,thereby inefficiently dissipating the energy.

The unit with the constantly decreasing orifice is an improvement overthe unit having the fixed orifice because, if the velocity of the massdecreases during the dissipation of the kinetic energy, the orifice sizealso decreases, thereby theoretically maintaining a constant reactiveforce on the mass. However, the drawbacks of this type includes the factthat the unit could still exert too large a force on the mass or, if theorifice is .sized for the greatest velocity which is to be expected,then, in practice, the velocity will be somewhere below this value;thus, the reactive force exerted on the mass will be less than isneeded. Therefore, the energy dissipation will be, again, inefficient.In both the foregoing cases, the efficiency of the system is directlyrelated to the velocity of the mass.

SUMMARY OF THE INVENTION The apparatus of the present invention avoidsthe problems associated with the use of conventional structures of thetype described because it operates to maintain a constant resistance orreactive force on a moving mass regardless of the velocity thereof. Thisreactive force or resistance is predetermined and based upon the forcewhich can be safely applied to the structure defining such mass. Theapparatus includes a hydraulic buffer in which resistance or a reactiveforce developed thereby is directly related to a hydraulic pressuretherein. Moreover, the apparatus includes means defining an annularorifice which is adjusted automatically to maintain a constant pressuredrop across the buffer regardless of the velocity of the moving massagainst which the reactive force is exerted.

The system is operable to dissipate a major portion of the energy of themass with only a small portion of the energy being stored. Theresistance or reactive force of the apparatus is substantially constantnot only with respect to velocity but with respect to the position ofthe displacement stroke of the buffer. Also, the apparatus operates toabsorb the maximum amount of en ergy throughout its entire stroke.

The apparatus further operates to restore the buffer to an initialoperating position by utilizing the stored energy to reset the buffer.Thereafter, the apparatus is ready for receiving another shock appliedby a moving mass.

The primary object of this invention is to provide an improved shockabsorbing apparatus suitable for dissipating the kinetic energy of largemasses wherein the apparatus operates to provide a substantiallyconstant reactive force or resistance to a moving mass while dissipatingits kinetic energy, with the force being independent of velocity anddisplacement of the moving parts of the apparatus during the energydissipation interval.

Another object of this invention is to provide an apparatus of the typedescribed wherein the apparatus includes components which effectivelydissipate the kinetic energy of a moving mass yet allows a small portionof the energy to be stored so that such stored energy can be used toreset the apparatus to its initial operating condition after the kineticenergy of the mass has been fully dissipated.

Still another object of this invention is to provide apparatus of theaforesaid character wherein a loadreceiving buffer is coupled by valvemeans to a fluid accumulator so that energy is dissipated in the valvemeans and the connecting lines and is partially stored in an accumulatorso that the energy will be effectively dissipated yet the stored energyof the accumulator can be used to reset the buffer to its initialposition, ready to receive the shock loads of another incoming mass.

Other objects of this invention will become apparent as the followingspecification progresses, reference being had to the accompanyingdrawing for an illustration of the invention.

In the drawing:

FIG. 1 is a schematic view of the apparatus of this invention, showingthe force-receiving buffer thereof in the form of a fluid piston andcylinder assembly coupled by valve means to a fluid accumulator;

FIG. 2 is a graphic view of the force-displacement characteristic of thebuffer; and

FIG. 3 is a cross-sectional view of an embodiment of the valve used tointerconnect the buffer and the accumulator.

The apparatus of this invention is broadly denoted by the numeral 10 andis illustrated in FIG. 1. Apparatus 10 includes a buffer 12 having acylinder 14 provided with a piston 16 shiftably mounted therewithinbetween a pair of opposed end walls 22 and 30 of the cylinder. A shaft18 secured to piston 16 extends through an opening 20 in end wall 22 andprojects outwardly therefrom. A pad 24 is pivotally or otherwise coupledto the outer end of shaft I8 and is provided with a flat, outer surface26 which is adapted to be engaged by a moving structure defining a masswhose kinetic energy is to be dissipated by apparatus 10. Cylinder 14has plate means 28 coupled to end wall 30 for attachment in any suitablemanner to a mounting plate 32 on a rigid support 34, such as a wall,dock or the like.

Cylinder 14 has a chamber 36 between piston 16 and end wall 30. Thischamber is adapted to contain a hyraulic fluid and varies in volume inresponse to the movement of piston 16 relative to cylinder 14. Thecylinder has a fluid flow passage 38 through its sidewall incommunication with chamber 36.

A fluid accumulator 40 also forms a part of apparatus 10. Accumulator 40has an inlet which is coupled by a first flow line 42, a valve 44 and asecond flow line 46 to passage 38. Valve 44 operates to allow fluid flowfrom chamber 36 to accumulator 40 when piston 16 moves to the left whenviewing FIG. 1,i.e., during a displacement stroke of buffer 12. Thus,lines 42 and 46 and valve 44 form a first fluid flow path between thebuffer and the accumulator."-

A second fluid flow path is provided between buffer 12 and accumulator40 in bypassing relationship to valve 44. This second path includes afluid flow line 48 coupled to a flow line 46, a flow control valvedevice 50, and a check valve 52 of the type which allows flow of fluidonly in a direction from the accumulator to the buffer. A flow line 54connects check valve 52 with line 42. Flow control valve device 50 canbe eliminated if it is not considered necessary.

Valve 44 operates to maintain a constant fluid pressure within chamber36 regardless of the velocity of piston 16 and regardless of itsposition relative to cylinder 14. To this end, valve 44 has an outerhousing 56 (FIG. 3) provided with an inlet opening 58 coupled to fluidflow line 42. Fluid from chamber 36 and line 42 enters housing 56 andpasses into an outer chamber 60, passing thereafter through an orifice62 in an annular extension 63 of a shiftable valve member 65 shiftablycarried within a bore 67 in a fixed body 69 within housing 56.

Fluid passing through orifice 62 enters a chamber 64 in body 69. Chamber64 is in fluid communication with a pilot relief valve 66 throughpassages 68 and 70. Valve 66 has a shiftable valve member 71 which isbiased -toward a closed position by a coil spring 72. The fluid passingthrough valve '66 enters the central bore 73 in extension 63 of valvemember 65, the latter being biased by a coil spring 75 into closingrelationship to an outlet orifice 76 in body 69. Valve member 65 alsohas a fluid passage 78 therethrough which permits any excess hydraulicfluid to pass into a region 80 exteriorly of body 69 and communicatingwith line 46 through an outlet opening 82.

As pilot relief valve member 71 opens, there is a pressure drop betweenchambers 60 and 64, the higher pressure being in chamber 60. Such higherpressure thereby exerts a force on the annular face 84 of valve member65, thereby causing the latter to be moved to the left when viewing FIG.3 and out of engagement with the valve seat 86 at the entrance oforifice 76. Fluid flowing into chamber 60 can then pass through orifice76 and out of valve 44 to line 46.

During use, apparatus is mounted on support 34 such as in the mannershown in FIG. 1. Piston 16 will have an initial position within cylinder14 by virtue of a predetermined volume of hydraulic fluid, such as oil,in chamber 36. Valve 44 will, of course, be closed because valve member65 will close orifice 76 under the bias force of spring 75. Chamber 60of valve 44 will also contain fluid by virtue of its communication withchamber 36.

When a mass strikes pad 24, shaft 18 will be forced into the cylinder,causing piston 16 to move to the left when viewing FIG. 1. This willcause an increase in fluid pressure in chambers 36 and 60. Chamber 64,also in fluid communication with chamber 60, will experience an increasein pressure until the pressure increase exceeds the bias force of spring72, whereupon valve 66 will open, causing the fluid pressure in chamber64 to drop with respect to that in chamber 60. Thus, the unbalancedforce due to the variation in fluid pressures in chambers 60 and 64 willcause valve member 65 to unset with respect to valve seat 86, therebyopening the fluid passage defined by orifice 76. Fluid will then flowfrom chamber 60 through orifice 76, into region 80, through line 46 toaccumulator 40. The accumulator will then be pressurized by the incomingfluid thereto so as to store a portion of the energy in the form offluid pressure, such stored energy representing a portion of the energyof the mass striking pad 24.

Pilot relief valve 66 and orifice 62 are selected as to size so that arelatively constant pressure is maintained in chamber 60 regardless ofvelocity or stroke of piston 16. For instance, if the fluid pressurecommences to rise in chamber 60, valve member 62 shifts to the left whenviewing FIG. 3, to open or increase the effective opening of orifice 76,thereby causing a decrease in the pressure in chamber 60 and ultimatelymaintaining the pressure at a desired level, i.e., corresponding to aconstant reactive force exerted by the hydraulic fluid on piston 16.Conversely, if the pressure in chamber 60 commences to drop, valvemember 65 shifts to the right when viewing FIG. 3 under the influence ofcoil spring 75, thereby reducing the orifice size of orifice 76. Thisreduction in fluid pressure in chamber 60 thereby effectively provides aconstant force exerted by the hydraulic fluid in chamber 36 againstpiston 16.

A small amount of the incoming energy is stored in accumulator 40. Atthe end of the stroke of piston 16, valve 44 closes becausethe fluidpressures in chambers 60 and 64 are equalized due-to the fact that nofurther positive displacement of piston 16 occurs. The fluid underpressure in accumulator 40 representing the stored energy thereof thenflows in bypassing relationship to valve 44 through line 48, controlvalve device 50, valve 52, line 54 and back to fluid flow passage 38into chamber 36. This increases the pressure of chamber 36, causingpiston 16 to move to the right when viewing FIG. 1 and causing it to bereset to its initial starting position. Thus, apparatus 10 is then readyto absorb the energy of another moving mass striking pad 24.

Apparatus 10 operates to provide a substantially constant resistance toreactive force to a moving mass in engagement with pad 24 regardless ofthe velocity of the mass and irrespective of the position of piston 16along its stroke. Valve 44, defining a relief valve, provides the majorportion of the aforesaid resistance. While the resistance provided by arelief valve is relatively constant compared to a spring or an orifice,it is not completely insensitive to velocity changes. This velocityvariation can be kept small, however, by proper choice of valve 44. Apilot operated relief valve is the preferred type and may have as littleas 5 percent variation in resistance pressure between minimum andmaximum velocity. However, the system of apparatus compensates for suchvariations.

The resistance of buffer 12 is comprised of the pressure drop of valve44, pressure drop in fluid flow lines 42 and 46, and the fluid pressuredeveloped in accumulator 40. As the buffer is actuated by the load,energy is dissipated and velocity decreases. Resistance of valve 44drops slightly as the velocity decreases, the pressure drop inconnecting pipes and lines also reduces as the velocity decreases.Accumulator pressure increases during this time and adds to theresistance. Proper selection of accumulator size and by providing a gasprecharge therefor will result in a buildup of accumulator pressure soas to maintain a substantially constant total resistance pressure.

Apparatus 10 is essentially an energy dissipating system with only asmall portion of the energy being stored. Precharging of the accumulatorto slightly more gas pressure than required to overcome bufferrestoration assures that there will always be enough pressure availableto reset the buffer. The accumulator size is selected such that, ashydraulic fluid is forced into it, the pressure increase equals thedecrease in the valve and line resistance due to velocity decrease.

The operating characteristic of apparatus 10 is shown in FIG. 2, whereinthe force exerted on piston 16 by the fluid in chamber 36 is representedby being constant afer a predetermined plateau has been reached. Thisplateau, represented by curve 90, is reached when the fluid pressure inchamber 36 and thereby lines 42 and 46 and chamber 60 builds upsufficiently to cause pilot relief valve 66 to open. Thus, any furtherpressure increase will cause the main valve member 65 to open.Thereafter, variations in the fluid pressure due to velocity ordisplacement changes of piston 16 are compensated for by further openingor closing of valve member 65 relative to orifice 76. Thus, the systemcharacteristic of FIG. 2 represents the way in which apparatus 10operates regardless of velocity or displacement changes of piston 16.

I claim:

1. Energy absorbing apparatus comprising: a fluid buffer having a first,fixed, hollow part adapted to contain a hydraulic fluid and a secondpart mounted on the fixed part for movement relative thereto, saidsecond part adapted to be engaged by a moving mass and to be shiftedthereby relative to said first part in one direction to exert a force onthe fluid therein; a fluid accumulator exterior of the buffer; meansforming a first fluid flow path between said first part and saidaccumulator; means in said first path for defining a resistance to theincrease of pressure in said first path after the pressure therein dueto the force exerted by said second part on said fluid has reached apredetermined value; and means in bypassing relationship to saiddefining means for presenting a second fluid flow path to allow fluiddirected to the accumulator along said first path to return to saidfirst part, to thereby urge the second part in the opposite directionwhen the effect of the movement of said moving mass has been removedtherefrom.

2. Apparatus as set forth in claim 1, wherein said dcfining meansincludes a relief valve adapted to be opened and to maintain the fluidpressure in said first part at said predetermined value forsubstantially all values of velocity and operative positions of saidsecond part relative to said first part.

3. Apparatus as set forth in claim 2, wherein said valve is of thepilot-actuated type.

4. Apparatus as set forth in claim 1, wherein said buffer comprises afluid piston and cylinder assembly.

5. Apparatus as set forth in claim 1, wherein said presenting meansincludes a fluid flow line having a check valve therein which permitsfluid to flow only from the accumulator to said first part.

6. Apparatus as set forth in claim 1, wherein the ac cumulator isprecharged with a fluid.

7. Apparatus as set forth in claim 1, wherein the said forming means,said defining means and the accumulator are separate from said buffer.

8. Apparatus as set forth in claim 1, wherein is included a secondbuffer having a first, fixed, hollow part adapted to contain a hydraulicfluid and a second part disposed in and movable relative to the firstpart to exert a force on the fluid therein, said first part of thesecond buffer being in fluid communication with said forming means.

9. Apparatus as set forth in claim 1, wherein said defining meansincludes a valve having a main valve portion and a pilot relief valveportion, said main valve portion being opened by fluid pressure in saidfirst path only after said pilot relief valve portion has been opened.

10. Apparatus for absorbing the kinetic energy of a moving masscomprising: a fluid piston and cylinder assembly having means thereonfor mounting the same in a support, the piston of the assembly beingshiftable longitudinally of the cylinder thereof and having a shaftextending through the cylinder and projecting outwardly therefrom, theouter end of the shaft having a pad adapted to be engaged by a movingmass, the cylinder having a chamber remote from said shaft andcontaining a hydraulic fluid, there being a fluid passage through thecylinder in fluid communication with said chamber thereof, said pistonbeing operable to pressurize the fluid in said chamber when a movingmass engages and moves said pad and thereby said piston in onedirection; a fluid accumulator exteriorly of the assembly and adapted tobe pressurized by fluid received thereby, whereby the accumulator canstore energy in the form of fluid pressure; means defining a first fluidpath between said fluid flow passage of the cylinder and theaccumulator; a pilot-actuated relief valve disposed across said firstpath and being normally closed when the piston is in an initialoperative position within the cylinder, said relief valve being openedwhen the fluid pressure in said first path has attained a predeterminedvalue, said valve having means for maintaining the fluid pressure insaid first path substantially constant for substantially all velocitiesand operative positions of the piston relative to the cylinder; a checkvalve; and means forming a second fluid flow path for coupling the checkvalve to the accumulator and to said fluid flow passage to permit returnof fluid from the accumulator to said chamber after the piston movementin said one direction has been halted to thereby cause the piston tomove in the opposite direction toward and into said initial operativeposition.

11. Apparatus as set forth in claim 10, wherein the relief valve has apilot relief valve portion and a main valve portion, the main valveportion being opened only after the pilot relief valve portion has beenopened, and including means on the relief valve portion for biasing thesame to a closed position, and means for adjusting the bias force ofsaid bias means.

12. Apparatus as set forth in claim 10, wherein is included a fluid flowcontrol valve device coupled to said second path in series relatinshipwith the check valve.

1. Energy absorbing apparatus comprising: a fluid buffer having a first,fixed, hollow part adapted to contain a hydraulic fluid and a secondpart mounted on the fixed part for movement relative thereto, saidsecond part adapted to be engaged by a moving mass and to be shiftedthereby relative to said first part in one direction to exert a force onthe fluid therein; a fluid accumulator exterior of the buffer; meansforming a first fluid flow path between said first part and saidaccumulator; means in said first path for defining a resistance to theincrease of pressure in said first path after the pressure therein dueto the force exerted by said second part on said fluid has reached apredetermined value; and means in bypassing relationship to saiddefining means for presenting a second fluid flow path to allow fluiddirected to the accumulator along said first path to return to saidfirst part, to thereby urge the second part in the opposite directionwhen the effect of the movement of said moving mass has been removedtherefrom.
 2. Apparatus as set forth in claim 1, wherein said definingmeans includes a relief valve adapted to be opened and to maintain thefluid pressure in said first part at said predetermined value forsubstantially all values of velocity and operative positions of saidsecond part relative to said first part.
 3. Apparatus as set forth inclaim 2, wherein said valve is of the pilot-actuated type.
 4. Apparatusas set forth in claim 1, wherein said buffer comprises a fluid pistonand cylinder assembly.
 5. Apparatus as set forth in claim 1, whereinsaid presenting means includes a fluid flow line having a check valvetherein which permits fluid to flow only from the accumulator to saidfirst part.
 6. Apparatus as set forth in claim 1, wherein theaccumulator is precharged with a fluid.
 7. Apparatus as set forth inclaim 1, wherein the said forming means, said defining means and theaccumulator are separate from said buffer.
 8. Apparatus as set forth inclaim 1, wherein is included a second buffer having a first, fixed,hollow part adapted to contain a hydraulic fluid and a second partdisposed in and movable relative to the first part to exert a force onthe fluid therein, said first part of the second buffer being in fluidcommunication with said forming means.
 9. Apparatus as set forth inclaim 1, wherein said defining means includes a valve having a mainvalve portion and a pilot relief valve portion, said main valve portionbeing opened by fluid pressure in said first path only after said pilotrelief valve portion has been opened.
 10. Apparatus for absorbing thekinetic energy of a moving mass comprising: a fluid piston and cylinderassembly having means thereon for mounting the same in a support, thepiston of the assembly being shiftable longitudinally of the cylinderthereof and having a shaft extending through the cylinder and projectingoutwardly therefrom, the outer end of the shaft having a pad adapted tobe engaged by a moving mass, the cylinder having a chamber remote fromsaid shaft and containing a hydraulic fluid, there being a fluid passagethrough the cylinder in fluid communication with said chamber thereof,said piston being operable to pressurize the fluid in said chamber whena moving mass engages and moves said pad and thereby said piston in onedirection; a fluid accumulator exteriorly of the assembly and adapted tobe pressurized by fluid received thereby, whereby the accumulator canstore energy in the form of fluid pressure; means defining a first fluidpath between said fluid flow passage of the cylinder and theaccumulator; a pilot-actuated relief valve disposed across said firstpath and being normally closed when the piston is in an initialoperative position within the cylinder, said relief valve being openedwhen the fluid pressure in said first path has attained a predeterminedvalue, said valve having means for maintaining the fluid pressure insaid first path substantially constant for substantially all velocitiesand operative positions of the piston relative to the cylinder; a checkvalve; and means forming a second fluid flow path for coupling the checkvalve to the accumulator and to said fluid flow passage to permit returnof fluid from the accumulator to said chamber after the piston movementin said one direction has been halted to thereby cause the piston tomove in the opposite direction toward and into said initial operativeposition.
 11. Apparatus as set forth in claim 10, wherein the reliefvalve has a pilot relief valve portion and a main valve portion, themain valve portion being opened only after the pilot relief valveportion has been opened, and including means on the relief valve portionfor biasing the same to a closed position, and means for adjusting thebias force of said bias means.
 12. Apparatus as set forth in claim 10,wherein is included a fluid flow control valve device coupled to saidsecond path in series relatinship with the check valve.